Art of refining hydrocarbons



June 30, 1931. E. w. lsoM ART OF REFINING HYDROCARBONS Fild Feb. 29. 1928 Patented June 30, -1931 i UNITED STATES PATENT OFFICE EDWARD W. ISOM, OF SCARSDALE, NEW IYORK, ASSIGNOR TO SINCLAIR REFINING COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF MAINE ART OF REFINING HYDROCARBONS Application led February 29, 1928. Serial No. 257,959.

This invention relates to improvements in the refining of cracked gasoline, particular 1y gasoline produced by vapor phase cracking, intended for use as motor fuel. l

Certain unsaturated constituents or aromatic constituents of cracked gasoline, particularly gasoline produced by vapor phase cracking, have anti-knock properties and therefore are of special value as components of motor fuel gasoline. However, cracked gasoline, particularly gasoline produced by vapor phase cracking, usually includes other unsaturated constituents, such as the di-olenes, which are undesirable as components of motor fuel gasoline because of instability, bad color or bad odor.

Such undesirable constituents can be selectively polymerized by passing vapors containing them through an adsorptive catalyst, such as fullers earth, under appropriate conl ditions to form polymers of boiling point higher than the original constituents and such polymers can then be separated from the vapors, for example, by fractional condensa-tion.

This general method of refining hydrocarbon vapors, by passing the vapors through an adsorptive catalyst, is Well known, but its use in the refining of raw cracked gasoline involves several peculiar difficulties because cracked gasoline, particularly gasoline produced by vapor phase cracking, usually includes a relatively large proportion of highly reactive unsaturated constituents. All of these highly reactive constituents are not objectionable but many are of special value l as components of motor fuel gasoline, as noted v ponents of the gasoline product is usually encountered. The polymerization reaction is When hydrocarbon vapors containing alarge proportion of such reactive constituents are passed through such adsorptive catalysts, excessive polymerization and consequent loss of constituents desirable as comexothermic and this, as well as the proportion of reactive constituents present, probably promotes this tendency toward excessive polymerization. Such losses are peculiarly important because they are losses of constim` to fractionating operations, for example, for

the direct production of motor fuel gasoline of definite end boiling point. This loss also may be due to excessive polymerization, poly merization induced by the maintenance of the vapors at elevated temperature for a substantial period of time in the fractioning operation.

This invention provides a particularly advantageous method of refining the vapor of cracked gasoline, particularly gasoline produced by vapor phase cracking. The invention also provides a combined cracking and refining operation particularly advantageous for the production of motor fuel gasoline.

According to the present invention, the cracked gasoline vapors are passed through an adsorptive catalyst, such as fullers earth, in admixture with a substantial proportion of vapors of higher boiling hydrocarbon constitutents and the vapor mixture escaping from the refining operation is then subjected to a fractionating operation to condense therefrom all constituents of boiling point higher than suitable as components of the desired gasoline product. The composition of the vapor mixture supplied to the refining operation should be such that condensed it forms a condensate containing not less than about 50% and not more than 75%l of the desired gasoline product, or better not less than about and not more than 70% of the desired gasoline product. The most advantageous gasoline concentration Will vary, but for the production of motor fuel gasoline, of end boiling point approximately Within the range of 390411400 F.; it comes Within these limits.

In the combined cracking and refining operation of the invention, vapors including vapors of the gasoline product are taken oif from the cracking operation proper, if neces-v sary these vapors are subjected to a preliminary fractionating operation to bring the concentration of gasoline components in the remaininglvapor mixture Within the desired limits, the gasoline-containing vapors lare then passed through a charge of an adlsorptive catalyst such as fullers earth, the vapors escaping from this refining operation are then subjected to a fractionating operation to condense all constituents of boiling point, higher than suitable as components of the gasoline product, and' the vapors escaping from this fractionating operation are condensed to form the gasoline product. A subthe cracking operation and the refining operation from which condensate is returned to the cracking operation to strip it of any low boiling constituents before the higher boiling portions are returned to the cracking operation.

While the invention is of special value and application in connection with vapor phase cracking operations, it is generally useful in lconnection with cracking operations of the several known types, but particularly where the vapor mixture from the cracking operation includes a relatively large proportion of highly reactive unsaturated constituents.

The invention makes possible an increase in the production of motor fuel gasoline of as muchas 100% or more, particularly as compared to operations otherwise'similar except in that the gasoline is frictionated directly to the end boiling point desired before being passed through the adsorptive catalyst and particularly where the condensates higher boiling than the gasoline product are returned to the cracking operation.

The invention is not predicated upon any explanation ot the results obtained but upon the results themselves, but there are a number of factors which may contribute to the improved results which are obtained. Apparently, the dilution of the gasoline vapors during contact with the adsorptive catalyst tends to minimize excessive polymerization in the'rening operation proper and in the subsequent fractionating operation, the more reactive constituentshaving been removed orrendered relatively inactive by polymerization, the reduced concentration of highly rev active rconstituents tends again to minimize objectionable polymerization. The presence i of higher boiling constituents in the vapor mixture subjected to the refining operation proper tends to maintain a higher mean tem.- perature in the refining operation; this high.- er temperature in conjunction with the dilution of the gasoline vapors may improve the refiningy operation itself, and this higher temperature may avoid losses due to separation of low boiling constituents with higher boiling polymers produced by the vaporcatalyst contact, particularly where such higher boiling material is returned to the cracking operation. The higher boiling constituents present in the vapor mixture may also act as a distilling medium stripping from the higher boiling polymers produced by the vapor-catalyst Contact any dissolved or en- Y trained low boiling constituents. Where the vapor mixture is fractionated to the final end boiling point before being passed in contact with the adsorptive catalyst some of the constituents polymer-ized in the refining operation of this invention may be condensed unpolymerized in the ractionating operation, and itv is possible that such constituents in that form may have some high solvent capacity for low boiling constituents desirable as components of the gasoline product.

The invention will be further described in connection with the accompanying drawings which illustrate, diagrammatically and conventionally, one form of apparatus adapted for. carrying out-the invention. It will be understood that the exact form of the apparatus used is not essential to the invention The cracking apparatus illustrated, the heating coil 1, the digesting chambers 2 and the tar separating tower 3, are of the type described by Harry L. Pelzer for carrying out vapor phase cracking operations in an application iiled June 13, 1927, Serial No. 198,621.V The invention is of special value and application in connection with tAhe operation of such vapor phase cracking apparatus.

As an example of the operation of this cracking apparatus, a gas oil fraction 1s supplied to the heating coil 1, the oil is vaporized thereiny and the vapors superheated to a temperature in the neighborhood of 1,000- 1,500 F., these superheated vapors are passed through the digesting chambers 2 Jfrom which they are discharged 'at a-temperature in the neighborhood of 900-1,0 00 F., the vapors discharged from the digesting chambers are freed of entrained tarry matter in the scrubbing tower 3, and the remaining vapors are then passed on to further fractionating and refining ope-rations.

The separation of tarry matter in tower3 is effected by scrubbing the vapors therein, for example, with fresh-stock or with condensate from some subsequent ractionating operation supplied through connection 18, or

by recirculating liquid tar through connec- 13e tion 17. Where vfresh stock or a condensate suitable to* be supplied to the heating coil 1 is used as a scrubbing agent, the rate at which it is supplied is regulated so that'the stock, or so much of it as is free from tarry matter, is vaporized to escape to some subsequent -fractionating operation from which conthe scrubbing agent, the operation may be densate. Iis returnedA to the heating coil 1. Where part of theyseparated tar is used as regulated by cooling oi' partially cooling this tar, or so muchof it as is reintroduced into the tower, before reintroduction. The separated tar is discharged through bonnection 19.

lThe-raw cracked gasoline-containing vapors v tration in the vapor mixture within the limits previously mentioned' is condensed. This v .operation maybe controlled, for example, by

the regulated introduction'of fresh stock or of'ycondensate from a subsequent fraction- 'ating operation throughl connection v6. The

. remaining vapornmixture escapes through connections-7 and'8 to the-#refining .tower 9.

:Q If the concentration of, gasoline components in the vapor mixture escaping from the' -cracking operation through connection 4 is unsuitable as components of the gasoline within the desired limits, this vapor mixture maybe supplied directly tothe refining tower 9 through .connections 10 and 8.

InA the refining tower 9, the vapor mixture supplied through connection 8 is passed through ach'arge, :for example, of fullers earth of 40-6O or 60- 80 mesh and those unsaturated constituents of the vapor mixture c product but falling within its boiling range are polymer-ized to form higher boiling polyy mers. A part of these higher boiling poly-1 mers may be se ara-ted from the vapor mixture in the re ning towerf and' dischargedv therefrom through connection 11b The gasoline-containing vapors escape through connection 12 to the .fractionating tower .13

where all -constituents of the vapor mixture of boiling point higher than suitable as components'of the gasoline product, including. any remaining -higher boiling polymers produced .in the refining operation, are

condensed. The condensate is discharged 'through connection 14.' The remaining gaso.

line vapors escapel through connection 15 to the condenser 16 where they are condensedto form the gasoline product. The gasoline condensate is separated from any uncondensed vapors and gases inthe receiver 20. The condensed gasoline product is discharged from this receiver through connection 21 and uncondensedvapors and. gases through conn ectionv 22. The fractionating operation car-7 ried out ir tower- 13 may be controlled, forv example, by the reintroduction of part of the `gasoline condensate through .connection 28, or this operation may Vbe controlled by the regulated introduction ofv a gasoline fraction from some other source as described in` my application -led July 21, 1927, Serial No. 207,476.

The condensate'separated from the gasoline-containing vapors in the fractionating tower 18 is with advantage returned to the cracking operation. This condensate, for example, may be returned directly to the heating coil l'through connections 18, 24 and 25,- or this( condensate or part of it may be introduced into theA scrubbing towerv 3 through connections 14, 24 and 18 to control or assist in controlling the scrubbing operation in -admixture with'the condensate trom tower 5'. The higher boiling polymers separated in the refining -tower 9 and discharged through connection-11 may be handled in the same manner as the condensate discharged from tower 13. Where the major portion of the higher boiling polymers produced 'by the vaor-catalystcontact' are separated Ainwthe re ning tower 9, it is advantageous to intro.

duce the material liquefied in this tower into vthe scrubbing tower 3, through connections 11,28 and l18. t f

Rawstock to be supplied to the cracking operation may be supplied directly to the heating coil 1 throughn connection 25, or it may be introduced into the scrubbing tower 3 through connection 18 or into the. fractionating tower 5 through connection 6, or it-may be supplied to the operation in part in any two or more of these wa s. 1 Y

In. carrying out the ,invention in the apparatus illustrated, the products of the vapor phase cracking operation which normally in trolled to maintain the composition of the,

the desired gasoline product, the remaining vapor mixture including vaporsof the desired gasoline product diluted with higher boiling hydrocarbon constituents is then passe through fullers earth or other similar adsorptive catalyst in the refining tower 9, thevapor mixture escaping from this refining operation is 'then subjected to a fractionating operation in tower 13 to condense all constituents of boiling point higher thansuitable as components of the gasoline product, and the vapors escaping from this ractionating operation are condensed to form the gasoline product. In one sense, the reiining operation includes the passage of the hydrocarbon vapors through theadsorptive catalyst and also the subsequent Airaictionating operation since a part at least of the higher boiling polymers produced by the vapor-catalyst contact are separated 'in the subsequent fractionating operation, but in carrying out the present invention higher boiling constituents s other than those passed through the adsorpv Ytive catalyst as' part of the gasoline-contain- :imgasoline which comprises passing the gasoing vapor mixture are also separated from densate containing not less than about 50% and not more than 75% of the, gasoline product, condensing the constituents of the vapor mixture after passage through the adsorptive catalyst higher boiling than suitableas components of the gasoline product in a fractionating. operation, and condensing the vapors' escaping from this fractionating operation l prior to further cohtacts with the adsorptive catalyst to form the'gasolin'e roduct.

3. An improved method of producing gasoline which comprises taking olf from a cracking operation a vapor mixture including vapors of the gasoline product, bringing the concentration of gasoline components in this vapor mixture to a point such that condensed it forms a condensate containing not less than and not more than- 7 5% of the gasoline product, passing this gasoline-containing vapor mixture while at atemperature materially below the cracking tem erature through an adsorptivel catalyst, su jecting the vapor mixture remaining after passage through the adsorptive catalyst to a fractionating operation ,and therein condensing all constituents of boiling oint higher than suitable as components o the gasoline product, and condensing the remainingY vapors prior to further contact with the adsorptive catalyst to form the gasoline product.

4. An improved Jmethod of producing gasoline which comprises taking ofi from a crackv 4ing operation a vapor mixture including vapors of the gasoline product, bringing the concentration of gasoline components in this vapor mixture to a point such that condensed it forms a condensate containing not less than 50% and not more than 75% of the gasoline i product, passing this gasoline-containing vapor mixture while at a temperature materially below the cracking temperature through an adsorptive catalyst, subjecting the vapor mixture remaining after passage through the adsorptive catalyst to afraction- 'ating operation and therein-condensing all constituents'of boiling point higher than suitable as components of the gasoline product,

returning condensate produced in this 'frac-K tionating operation to the cracking operat1on,

and condensing the vapors escapmg from this fractionating operation prior to further,

contact with the adsorptive catalyst to form the gasoline product.

In testimony whereof, I have subscribed my name.

EDWARD W. ISOM.

2. The improvement in re ning cracked line in vapor phase but below the cracking temperature through an adsorptive catalyst in admixture with vapor'sof higher boiling hydrocarbons in proportions such that the vapor mixture when condensed forms a conv densate'icontaining not less'than about 60%' and not more than 70% of the gasoline prod- I uch-condensing, the constituents of the vapor mixture after passage through the adsorptive catalysthigher boiling than suitable' as components of the gasoline product in a fractionating operation, and condensing the vapors escaping vfrom this ractionating operation prior to further contact with the adsorptive catalyst to `form the gasoline product.

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